Elucidation of the various mechanisms responsible for fracture in different materials was the general subject of the Fourth Annual Symposium on Fundamental Phenomena in the Materials Sciences held January 31 and February 1, 1966, in Boston and sponsored by the Ilikon Corporation of Natick, Massachusetts. In an analysis of the brittle-to-ductile transition in polycrystalline metals, T. L. Johnston (Ford Motor Company) placed major emphasis on factors related to the plastic resistance associated with grain boundaries and the effects of plastic anisotropy. Utilizing a generalized form of the Griffith criterion, he said it can be readily shown that several individual factors may be made reasonably quantitative and that the nature of plastic response can be predicted. Specifically, it can be shown that a critical factor relates to the length of a plastic shear zone which is constrained by an elastically loaded matrix. As this length increases, the Griffith inequality is satisfied and brittle failure occurs; however, the use of decreased grain sizes or the refine ment of dislocation or twin distribution can further tend to "homoge nize" the plastic flow and to decrease the magnitude of the shear zone. Of considerable importance in the consideration of plastic resistance is the availability of favorably oriented slip systems in aa un sheared crystallite.

A physical, mechanism-based presentation of the plasticity and fracture of polymers, covering industrial scale applications through to nanoscale biofluidic devices.

Within the last two decades fracture theory has been one of the most rapidly advancing fields of continuous media mechanics. Noteworthy suc cess has been achieved in linear fracture mechanics where the propagation of the macrocrack in elastic materials is under study. However, fracture of materials is by no means a simple process since it involves fracture of structural elements ranging from atomic sizes to macrocracks. To obtain all information about how and why materials fail, all stages of the process must be studied. For a long time both mechanical engineers and physicists have been concerned with the problem of the fracture of solids. Unfortunately, most of their work has been independent of the others. To solve the problem not only requires the minds and work of mechanical engineers and physicists but chemists and other specialists must be consulted as well. In this book we will consider some conclusions of the "physical" and "mechanical" schools acquired by the A. F. Joffe Physics-Technical Institute of the USSR Academy of Sciences in Leningrad and the Institute of Polymer Mechanics of Latvian SSR Academy of Sciences in Riga. The methods for studying the phenomena of fracture applied at both Institutes are different yet complimentary to one another; the materials tested are also sometimes different.